1. Field of the Invention
This invention relates to an X-ray film feed speed control system in a dental radiographic apparatus for photographing the entire jaws.
2. Prior Art
In order to obtain a clear and sharp tomogram in the dental radiographic apparatus for photographing the entire jaws of the kind described, it is a general practice to change the rotatingly travelling speed of an X-ray generator moving along the dental arch, for example, with respect to the front teeth and to the back teeth to thereby control an X-ray dosage with respect to the front teeth and with respect to the back teeth. But it is necessary to synchronously change the speed of X-ray film feed in response to such control of X-ray dosage. To this end, it has heretofore been a general practice to provide a mechanism for changing an X-ray film feed speed in synchronism with the rotatingly travelling speed of the X-ray generator, increase the X-ray film speed when the moving speed of the X-ray generator is increased and the X-ray dosage with respect to each tooth is decreased, and reduce the X-ray film feed speed when the moving speed of the generator is decreased and the X-ray dosage with respect to each tooth is increased. But to facilitate diagnosis by making the desired region of the dental arch greater or smaller in magnification factor than the other regions thereof, it becomes necessary to change and control the X-ray film feed speed in the direction of higher or lower speed independent of the movement of the X-ray generator.